In the process of opening envelopes, many forms of devices, such as knife, saber or epee-like assemblies, have been employed to slit the flap edge of an envelope to permit access to the contents thereof. The use of such devices are inherently dangerous leading to cut and puncture type wounds through careless usage. In copending application, Ser. No. 239,459, there is disclosed a hand-held sheet material cutter comprised of a blade permanently secured in a solid holder and having a cutting edge thereof protruding a predetermined distance greater than the thickness of a sheet of material, such as paper to be cut but of a distance insufficient to effect cutting of a subadjacent sheet thereto.